ES2220164B1 - HYDRAULIC BRAKE SYSTEM FOR VEHICLES AND PROCEDURE FOR THE DETECTION OF GAS BUBBLES IN A HYDRAULIC BRAKE SYSTEM FOR VEHICLES. - Google Patents

Abstract

Installation of hydraulic brake for vehicles and procedure for the detection of gas bubbles in a hydraulic brake installation for vehicles, whose brake installation (10), especially electrohydraulic, comprises an external power source (12), in which they are connected one or several wheel brake cylinders (24). For the degassing of the brake fluid, the invention proposes to connect a gas separator (22) to the external power source (12), from which a degassing conduit (59) leads, in which a degassing valve is connected (56), towards a reservoir of brake fluid reserve (30). For degassing, the degassing valve (56) is opened for a short time. For the detection of gas bubbles in the brake fluid, the invention proposes a gas sensor (58), which has a throttle valve (60) and a pressure sensor (62) in the degassing duct (59).

Description

Installation of hydraulic brake for vehicles and procedure for detecting gas bubbles in a hydraulic brake installation for vehicles.

State of the art

The invention relates to an installation of hydraulic brake for vehicles according to the type of claim 1. On the other hand, the invention relates to a method for gas bubble detection in a brake installation hydraulic according to the type of claim 6.

Brake installations are known in themselves hydraulic for vehicles of the type indicated with a source of external hydraulic energy, usually a hydraulic pump. In the called electrohydraulic brake installations for vehicles, a necessary hydraulic braking pressure is generated for the braked with an external hydraulic power source and fed to one or several brake cylinders of the connected wheels. Usually, an external power source is connected hydraulic pressure accumulator, from which the liquid is extracted from necessary brakes, which is under pressure and is fed to the cylinders of wheel brake. A hydraulic braking pressure of the Wheels are regulated, in a specific way for each wheel individual, in each wheel brake cylinder depending on a theoretical value of the braking force, which is derived, for example, from a position of a brake pedal or a force exerted on the brake pedal. This pressure dependence of braking of the wheels with respect to the theoretical value of the force Braking does not necessarily have to be proportional. The pressure Wheel braking on wheel brake cylinders is regularly regulated with modulation valve arrangements of the braking pressure associated with each brake cylinder of the wheels. The energy required for braking comes from the electrohydraulic brake installations for vehicles, exclusively from the external power source, the brake pedal serves exclusively as a theoretical value sensor and is not involved in the formation of braking pressure. Sometimes with The brake pedal can generate brake pressure, through of a main brake cylinder, in the case of source failure External hydraulic power (auxiliary brake installation with muscular strength). An example of a brake installation electrohydraulic for vehicles of this type is disclosed in WO 98/28 174.

On the other hand, brake installations are known hydraulic for vehicles with hydraulic force amplification of braking In these vehicle brake installations, generates, for example with a brake pedal and a main cylinder brake, a hydraulic braking pressure, which is raised by a external hydraulic power source and is fed to the wheel brake cylinders. The braking pressure of the Wheels are formed, therefore, partly by muscle strength.

In principle, in all brake installations Hydraulic vehicles may appear gas bubbles in the brake fluid, which lead to undesirable compressibility of the hydraulic fluid. For example, if a pressure accumulator of the hydraulic brake installation for vehicles is configured as a gas pressure accumulator with a membrane, which separates a gas from the brake fluid accumulator or accumulator, then a diffusion of the gas from the accumulator to through the membrane in the brake fluid. The gas is dissolved certainly first in the brake fluid, but if it increases the amount of gas diffused inside and cannot be dissolved anymore completely, it will escape out of the solution and form bubbles. Also in the case of a drop in liquid pressure hydraulic, dissolved gas can leak out of the solution, Bubble and form gas bubbles. In this case, the fall of the pressure does not have to be conditioned in any way by a vehicle brake installation failure, also the hydraulic fluid pressure fluctuations of the installation of vehicle brakes, common during operation, they can lead to a gas or bubble dissolved in the liquid of brakes. Also in the case of a pressure accumulator that presents a piston must have a gas inlet in front of the piston in the brake fluid. On the other hand, the source of energy  external can aspirate gas (air) and penetrate the liquid of brakes.

To avoid gas bubbles in the cylinders brake wheels, are provided in the brake installation of vehicles of WO 98/28174 already mentioned provisions of cylinder and piston for each wheel brake cylinder, which separate the brake fluid from the wheel brake cylinders  of the brake fluid from the external power source. The fountain external power drives the pistons of the provisions of cylinder and piston with pressurized brake fluid and pistons boost brake fluid from the brake cylinders of the wheels with pressure. In this way, the liquid gas bubbles of brakes from the external power source are kept away, certainly, of the wheel brake cylinders, but the Gas bubbles are not removed from the brake fluid of the external power source. Therefore, it is accepted that the liquid from  external power source brakes presents a compressibility due to gas bubbles. On the other hand, this solution is expensive due to the arrangement of cylinder and piston required for each wheel brake cylinder.

Document DE 36 33 341 C2 proposes feed, at the end of a push regulation, that is, after activation of wheel brake cylinders of powered vehicles that tend to slip (forced turn), the  brake fluid from these wheel brake cylinders to a reserve reservoir of brake fluid, where the dissolved gas may bubble and gas bubbles may appear from the liquid brakes. However, this solution has the disadvantage that only cylinder brake fluid is degassed from vehicle wheel brakes, remaining in the remaining installation of vehicle gas brakes dissolved and gas bubbles in the brake fluid. On the other hand, the degassing takes place only after a regulation of the thrust (regulation of drive slip), therefore extraordinarily rarely during use normal of a car.

Advantages of the invention

The hydraulic brake installation of the vehicle according to the invention with the features of claim 1 presents a gas separator, which is arranged between the source External power and wheel brake cylinders. He gas separator has a degassing connection, which It can close with a degassing valve. Preferably the degassing connection is initially closed and is open for degassing brake fluid. The fountain external power of the vehicle brake system according to the invention transports brake fluid to the gas separator, from which the brake fluid comes to stop the cylinder from wheel brakes The gas bubbling from the brake fluid and the gas bubbles are separated in the gas separator and are can let out through the opening of the valve degassing The invention has the advantage that it is eliminated brake fluid gas from vehicle brake system and a compressibility of the brake fluid can be counteracted due to gas bubbles contained in the brake fluid. Market Stall that the external energy sources of the brake installations electrohydraulic for vehicles usually transport "in circuit ", that is, they aspirate, after braking, again the brake fluid that comes from the brake cylinders of the wheels directly or indirectly, for example, from a tank of Reserve brake fluid and transport brake fluid again to a pressure accumulator and gas separator, all the brake fluid volume is conducted and degassed, during the usual running operation, through the separator of gas.

The dependent claims have as object configurations and advantageous developments of the invention indicated in the main claim.

According to claim 2, a gas sensor in the degassing connection region of the gas separator During the opening of the valve degassing can be checked with the gas sensor if gas comes out from the gas separator or if gas bubbles are contained in brake fluid, which comes from the gas separator. For the Therefore, with the gas sensor you can check if the liquid vehicle brake system brakes contains bubbles Of gas. If the portion of gas in the brake fluid is too much high or if bubbles appear too often, this allows deduce that there is a failure in the brake installation of the vehicle.

Claim 3 provides, as a gas sensor, a pressure sensor and a throttle valve. Since to resistance is modified through the throttle valve of brake fluid circulation, when brake fluid It presents gas bubbles, fits in the throttle valve,  When the brake fluid contains gas bubbles, a pressure different than when the brake fluid does not contain bubbles of gas. These different pressures are measured with the sensor Pressure. This configuration of the invention enables a favorable price configuration of the gas sensor with expense reduced.

Since from the degassing connection the gas separator does not normally only leave gas, but brake fluid, which contains gas bubbles or brake fluid without gas bubbles, claim 5 provides for conducting the liquid of brakes that leave from the gas separator with a conduit of degassing from the degassing valve towards a reservoir of brake fluid reserve of the installation of vehicle brake, where gas bubbles can leave from the brake fluid, before the brake fluid is sucked again by the external power source. In this way, the brake fluid remains in the brake system of the vehicle.

The process according to the invention with the characteristics of claim 6 serves to detect gas bubbles in the brake fluid, which comes out through the degassing connection of the gas separator. As sensor of gas serves the arrangement, explained above in relation to the claim 3 of a throttle valve and a sensor Pressure. With the pressure sensor a pressure is measured and evaluated or a brake fluid pressure curve that leaves from the gas separator through the degassing connection and that circulates through the throttle valve. The evaluation it consists especially of a comparison of the measured pressure and of the pressure curve, respectively, with a pressure and curve of the pressure, respectively, that reigns in the valve throttling when brake fluid is bubble free Of gas. In the event that the pressure and the actual pressure curve, respectively, deviate from this theoretical pressure and this curve from the theoretical pressure, respectively, the presence of gas bubbles in the brake fluid, which reduce the resistance of circulation of the brake fluid through the throttle valve and thus lead to a fall reduced pressure in the throttle valve. The evaluation is preferably done completely automatic through data processing, for example in a electronic brake system control device Hydraulic for vehicles.

The other dependent claims have as an object configurations and advantageous developments of procedure indicated in claim 6.

He drew

The invention is explained in detail below. with the help of an embodiment of the invention represented in the drawing. The unique figure shows a diagram hydraulic of a vehicle brake system according to the invention.

Description of the embodiment example

\hbox{frenos 30.}

The hydraulic brake installation for vehicles 10 according to the invention, shown in the drawing, is configured as an electrohydraulic brake installation for vehicles. The vehicle brake installation 10 has an external power source 12 for the formation of a brake pressure, necessary for braking, in a hydraulic fluid of the vehicle brake installation 10. The external power source 12 makes available a brake energy required for braking. The external energy source 12 comprises a hydraulic pump 14, behind which a check valve 16 is connected. For actuation of the hydraulic pump 14, the external energy source 12 has an electric motor 18. A suction side of the hydraulic pump 14 is connected in the reservoir of liquid reserve

 \ hbox {brakes 30.} 

In the external power source 12 are connected a pressure accumulator 20 and a gas separator 22. The pressure accumulator 20 is configured as an accumulator of membrane gas pressure in the exemplary embodiment represented and described. Obviously, they can also be used Other types of pressure accumulators. In the accumulator of pressure 20 is stored brake fluid that is under pressure to that at any time, also when the hydraulic pump 14 is stop, a sufficient amount of liquid is available pressure brakes for braking. Due to the pressure accumulator 20, the hydraulic pump 14 must not be operated constantly, but rather fill the pressure accumulator 20 until a value is reached upper pressure limit with brake fluid, when the pressure in the pressure accumulator 20 drops to a limit value lower default.

In the gas separator 22 are connected wheel brake cylinders 24, one of which is represents by way of example in the drawing. To each cylinder of wheel brake 24 is associated with a formation valve of the pressure 26 and a pressure reduction valve 28. Through of the pressure forming valve 26 the brake cylinders from wheels 24 to gas separator 22, a through the pressure reduction valve 28 are connected the brake cylinders of the wheels 24 to a reserve reservoir of brake fluid 30. Pressure forming valves 26 are configured as 2/2 proportional magnetic valves connected steps in their basic position. They have a valve integrated differential pressure 32, which can be traversed by the current in the direction of the wheel brake cylinder 24. Pressure reduction valves 28 are configured as 2/2 proportional magnetic valves closed in its basic position The pressure forming valve 26 and the pressure reduction valve 28 associated with each cylinder of wheel brake 24 form a valve arrangement of modulation of the brake pressure of the wheels, with which can control or regulate in a known way a pressure of the wheel brake on the wheel brake cylinder 24. Also the pressure modulation valve arrangements of wheel brake 26, 28 allow adjustment of the Slip, specific to each individual wheel, (regulation anti-lock, drive slip regulation and gear dynamics regulation) of one-wheel brakes known way itself.

A suction side of the hydraulic pump 14 is connected to the reserve reservoir 30 of brake fluid.

In each brake cylinder of the wheels 24 is connected a brake pressure sensor 34. As a transmitter of theoretical value for wheel braking pressure, the brake installation 10 for vehicles features a brake pedal 36, in which a pedal travel sensor 38 is connected. The braking pressure of the wheel, which can be measured with the pressure sensors 34, on the brake cylinders of the wheels 24 it is regulated based on a pedal travel measured with the pedal travel sensor 38, where the dependence of the wheel braking pressure can be proportional to the pedal travel, but it doesn't have to be necessarily. Instead of the pedal travel sensor 38 can find application also a pedal force sensor not shown or can be measure a pressure in a brake master cylinder 40, which can be activated with brake pedal 36. This is known in itself and, therefore, it is not explained here in detail.

The braking pressure of the wheels on the Wheel brake cylinders 24 is not formed with the cylinder main brake 40 but with the hydraulic pump 14 from the source of external energy 12. For performing auxiliary braking with muscle strength in the event of brake installation failure electrohydraulic 10 for vehicles, the braking pressure of the Wheels can be formed with the main brake cylinder 40. One Auxiliary brake installation required for this is known per se and, since it is not the object itself of the present invention is not represented and not explained in detail.

The reservoir of brake fluid 30 it is mounted on the main brake cylinder 40. To be able to determine if brake pedal 36 is activated, it is provided a brake light switch 42. For control and regulation, the Hydraulic brake installation of the vehicle features a device control electronic 44, which receives electrical signals from the pressure sensors 34 of the brake cylinders of the wheels 24, from the pedal travel sensor 38 and from the switch of the brake light 42 and controlling the electric motor 18 of the external power source 12 and the magnetic valves 26, 28 of the brake installation 10 of the vehicle.

The gas separator 22, which is represented in drawing as a symbol, can present, for example, a wall of separation 46, which divides the gas separator 22 into a chamber of input 48, connected to external power source 12, and in a output chamber 50, in which the cylinders of wheel brake 24. The two chambers 48, 50 of the separator gas 20 are connected beyond the separation wall 46 by means of a gas accumulation space 52. The space of gas accumulation 52 is located above in a position of use of the  gas separator 22, so that the gas bubbles that found in the brake fluid build up, through the influence of the force of gravity, in the space of gas accumulation 52 above the inlet chambers and of exit 48, 50. The separation wall 56 prevents circulation direct gas bubbles from the entrance to the exit of the gas separator 22. The gas separator 22 presents above, in its gas accumulation space 52, a degassing inlet 54. Obviously, instead of the gas separator 22 described, They can use gas separators of another type of construction.

In the degassing connection 54 of the gas separator 22 is connected a degassing valve 56. Degassing valve 56 is configured in the exemplary embodiment depicted and described of the invention as 2/2-step magnetic valve connected in its basic position no powered by current.

In the degassing valve 56 is connected a gas sensor 58, from which conducts a conduit of degassing 59 return to the liquid reserve tank of brake 30. The gas sensor 58 has a valve throttle 60 and a pressure sensor 62 at the entrance of the throttle valve 60. Pressure sensor 62 provides an electrical signal to the control apparatus 44. The pressure sensor 62 may be arranged in principle also in the region of the throttle valve 60, if this is possible from the point of view of the construction, or at the outlet of the valve choke 60; you can also find several application pressure sensors (not shown). It is also possible connect the gas sensor 58 in front of the valve degassing 56 instead of connecting it back as It represents.

For the degassing of the brake fluid from the hydraulic brake installation 10 for vehicles opens the degassing valve 56, so that liquid comes out of brakes through degassing connection 54 from the gas separator 22 and flows to the reservoir of liquid reserve brakes 30. If gas bubbles are contained in the liquid brakes, then these accumulate in the accumulation space of gas 52 of the gas separator 22 and exit, when the valve Degassing 56 is open, with brake fluid through of the degassing connection 54 and enter the tank brake fluid reserve 30. In the reserve reservoir of the brake fluid 30, the gas bubbles come out of the brakes, the hydraulic pump 14 sucks brake fluid free of bubbles of gas from the brake fluid reservoir 30. Precondition for degassing is that the liquid from brakes are under pressure in the pressure accumulator 20 or that the Hydraulic pump 14 transport brake fluid to gas separator 22, so that, with the degassing valve 56 open, exit brake fluid through degassing connection 54 from the gas separator 22. Degassing can be performed occasionally when closing or opening a door of the driver of a car equipped with brake installation 10 for vehicles or with the ignition connected.

For gas bubble detection, it is measured during degassing, with degassing valve 56 open, pressure and pressure curve, respectively, of brake fluid coming out through the connection of degassing 54 from the gas separator 22, in front of the throttle valve 60, with pressure sensor 62 of the gas sensor 58 and is evaluated in the control device 44. If the brake fluid has no gas bubbles, the pressure has a value and a pressure curve, respectively, determined. Yes the pressure and the pressure curve, respectively, in front of the throttle valve 60 deviate from the value and curve of the pressure, respectively, when the liquid is free of gas bubbles, this is an indication of the presence of gas bubbles in the brake fluid. It can be considered normal and tolerable a limited amount of gas bubbles in the liquid of brakes coming out of the gas separator 22 through the connection degassing 54. If the amount of gas bubbles exceeds a tolerable value or too many gas bubbles accumulate, inside of a certain time, in the accumulation space 52 of the gas separator 22, then you have to start from a failure of the brake installation 10 for vehicles and can be issued, by For example, an optical or acoustic alarm signal to a driver.

Since especially the output speed of the brake fluid from the gas separator 50 through the degassing connection 54 depends on the pressure in the gas separator 50 and the pressure in front of the valve throttling 60 depends again on the output speed, it measured with a pressure sensor 64, connected to the gas separator 22, also the pressure in the gas separator 22 and the pressure and the pressure curve, respectively, in front of the throttle valve 60 depending on the pressure in the gas separator 22.

For degassing the brake fluid and for the detection of gas bubbles in the brake fluid, it open the discharge valve 56 preferably only transient, especially for a short period of time and by way of of impulses, for example also with a sequence of impulses. The transient opening, especially as impulses of the degassing valve 56 causes pressure fluctuations and pressure peaks in the throttle valve 60 of the sensor gas with a characteristic curve when the brake fluid is free of gas bubbles. If this pressure curve is known, what which is possible without difficulty by means of measurement, you can easily determine a deviation from this curve pressure characteristic and in this way can be recognized With high reliability gas bubbles in the liquid.

Claims (9)

1. Installation of hydraulic brake for vehicles with an external hydraulic power source, in which one or more wheel brake cylinders are connected, characterized in that between the external power source (12) and the wheel brake cylinder (24) a gas separator (22) is connected, which has a degassing connection (54), which can be closed with a degassing valve (56). 2. Hydraulic brake installation for vehicles according to claim 1, characterized in that the brake installation for vehicles (10) has a gas sensor (58) in the region of the degassing connection (54) of the gas separator (22) . 3. Hydraulic brake installation for vehicles according to claim 2, characterized in that the gas sensor (58) has a pressure sensor (62) and a throttle valve (60), which are connected in front of or behind the degassing valve . 4. Hydraulic brake installation for vehicles according to claim 1, characterized in that a pressure accumulator (20) is connected between the external power source (12) and the gas separator (22). 5. Hydraulic brake installation for vehicles according to claim 1, characterized in that the brake installation for vehicles (10) has a degassing duct (59), which leads from the degassing valve (56) to a liquid reservoir of brakes (30). 6. Procedure for detecting gas bubbles in a hydraulic vehicle brake installation, characterized in that the vehicle brake installation (10) has a pressure-driven gas separator (22), with a degassing connection (54) , in which a throttle valve (60) and a pressure sensor (62) are connected, and because a pressure and a pressure curve are measured and evaluated, respectively, in the throttle valve (60). Method according to claim 6, characterized in that a pressure is further measured in the gas separator (22) and the pressure and pressure curve are evaluated, respectively, in the throttle valve (60) as a function of the pressure in the gas separator (22). Method according to claim 6, characterized in that the degassing connection (54) is only opened temporarily for the detection of gas bubbles. Method according to claim 8, characterized in that the degassing connection (54) is opened by impulses.